Sound motion picture apparatus



G. A. DEL. VALLE ISOUND MOTION PICTURE APPARATUS April 5, 1955 3Sheets-Sheet 1 Filed May 5, 1951 ATTONEY April 1955 G. A. DEL VALLESOUND MOTION PICTURE APPARATUS 3 Sheets-$heet 2 Filed May 5, 1951Eufllermn H. 35%311:

ATTORNEY April 5, 1955 e. A. DEL VALLE SOUND MOTION PICTURE APPARATUS 5Sheets-Sheet 5 Filed May 5, 1951 INVENTOR Guillermu H, del ValleATTORNEY United States Patent SOUND MOTION PICTURE APPARATUS GuillermoA. Del Valle, Merchantville, N. 1., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application May 5, 1951, Serial No.224,696

3 Claims. (Cl. 274-4) The present invention relates to sound motionpicture apparatus and more particularly to mounting means for soundtranslating devices used on such apparatus.

In the motion picture art, a film has been developed bearing a magneticsound track which has demonstrated desirable characteristics. However,in order to use this type film, conventional machines must be modifiedto the extent of incorporating a magnetic transducer in the soundsystem. Since some of the film used on these machines will be of thetype bearing the magnetic sound track and some will be of the typebearing the conventional optical sound track, the modification ofconventional machines to adapt them to use with the magnetic sound trackshould not be such as to prevent the machines from being used with theconventional or optical sound track. A system suitable for use witheither type film is shown and described in a copending application toMasterson, Ser. No. 124,470, filed October 29, 1949, now Patent No.2,605,364, issued July 29, 1952.

In that application there is described and claimed a sound system inwhich a magnetic transducer and a mirror are mounted on a bracket whichis secured to the machine in a position surrounding a sound drum. Themirror and the magnetic transducer are spaced about the bracket bysubstantially 90. The two elements are selectively moved into operatingposition by rotating the bracket through the 90 angle. In that system,when the transducer is in its operating position, the assembly is substantially rigid. That is to say, the relative radial position of thetransducer with respect to the outer surface of the sound drum is fixed.In the operation of the machine, the film is drawn around the sound drumso that the sound-track portion of the film overhangs the rear edge ofthe drum. Since the film is usually made of a flexible plastic, theunsupported sound-track frequently develops imperfections in the form ofwaves or undulations. If the relative position of the transducer and thesound drum are fixed, these waves will cause variations in the spacingbetween the sound-track and the transducer which may be converted intoundesirable amplitude variations in the signals.

Accordingly, it is an object of the present invention to provide animproved sound system for motion picture apparatus suitable for use withfilm bearing a magnetic sound-track.

It is another object of this invention to provide an improved soundsystem as set forth characterized in that means are provided forresiliently supporting a magnetic transducer in a position forengagement with the magnetic sound-track of a film.

A further object of the present invention is to provide an improvedsound system as set forth which is selectively adaptable for use withfilm bearing either a magnetic or an optical sound-track.

Still another object of this invention is to provide an improvedmounting means for a magnetic transducer.

It is a still further object of the present invention to provide animproved mounting means as set forth characterized in that thetransducer is resiliently supported.

Yet another object of this invention is to provide an improved mountingmeans as set forth characterized in that a transducer supported thereonmay be adjusted with respect to the sound-track on the film.

In accomplishing these and other objects, there has been provided, inaccordance with the present invention, a mounting bracket secured to themain body of a motion 2,705,640 Patented Apr. 5, 1955 picture machineadjacent to the sound drum thereof. An arm is mounted on the bracket forlimited pivotal movement at a point remote from the drum. The arm has aportion at the free end thereof extending between the drum and the mainbody of the machine, and partly into the drum. A magnetic transducer iscarried on that portion of the arm adjacent to the drum. Resilient meansare secured to the bracket and positioned to exert a biasing force onthe arm'for urging the transducer into resilient engagement with thesound-track of a film which is being advanced over the drum.

A better understanding of the present invention may be had from thefollowing detailed description when read in connection with theaccompanying drawings, in which:

Figure 1 is a partial perspective view of a motion picture projectorembodying the present invention. The exciter lamp assembly is shownopened for a better view of the sound system.

Figure 2 is a front view of a mounting means for a transducer and anoperating switch therefore constructed in accordance with the presentinvention. The device is shown in position for operation with a filmbearing an optical sound-track.

Figure 3 is similar to Figure 2 but shows the device in position foroperation with a film bearing a magnetic sound track.

Figure 4 is a top view of the mounting means shown in Figures 2 and 3,

Figure 5 is an end view of the mounting means, and

Figure 6 is a side view, partly broken away, of the operating switchassembly shown in Figure 3.

Referring now to the drawings in more particularity, there is shown anembodiment of the present invention as applied to a conventional motionpicture projector 2 in which a film 4 is pulled from a supply reel (notshown) by a sprocket 6 and advanced intermittently by a pulldownmechanism (not shown) through a projection gate 8, over a guide roller10, under a pressure roller 12, around a sound drum 14, over a filterroller 16, and around a. sprocket 17 to a take-up reel (not shown).

The mounting means for the signal translating apparatus, shown moreclearly in Figures 2-5, consists of a mounting bracket 18 which issecured to the frame of the machine. An aperture 20 near one end of thebracket is adapted to receive a shaft 22 upon which the sound drum 14 iscarried. To the opposite end of the bracket, remote from the sound drum,there is secured a pivot pin 24. An arm 26 is mounted, at one endthereof, on the pivot pin 24.

Surrounding the pivot pin, and between that pin and the arm there isplaced an eccentric sleeve 28. A pin 30 extends from the end of theeccentric sleeve into a complementary recess 32 in a knurled cap member34. The knurled cap member is secured to the pivot pin 24 by a screw 36.

On the bottom of the bracket 18 (as viewed in Figures 2 and 3) adjacentthe pivot pin 24 there is secured a folded leaf spring 38. The free endof the spring presses against an adjustable stop 40 on the arm 26. Thisstop may comprise, as shown, a screw 40 and a nylon unthreaded insert 42which is pressed into a suitable opening in the arm. By varying thelength of the stop, the pressure exerted thereon by the spring may beaccordingly adjusted. The free end of the spring is provided with aslight twist whereby the pressure exerted on the stop 40 has a componentof force in a crosswise direction to take up any play that may beintroduced by the tolerances in the assembly adjacent to the pivot pin24.

A screw 44 with an eccentric head 46 is attached to the bracket 18. Theeccentric head 46 extends through an elongated opening 48 in the arm 26.The threaded portion of the screw 44 extends through a second nyloninsert 50 which is securely imbedded in the bracket. The purpose servedby both of the nylon inserts 42 and 50 is to permit intentionaladjustments of the respective screw members, but, because of theirbinding action, to prevent a misadjustmcnt from occurring throughvibration of the apparatus, or the like.

The free end of the pivoted arm 26 is somewhat enlarged and is recessedon the top of the enlarged portion to contain a magnetic transducer unit52, preferably of the type shown and claimed in a copending applicationto Granthan, Serial No. 102,023, filed June 29, 1949, now Patent No.2,621,259, issued December 9, 1952. The transducer unit comprises a coreassembly 54 which, with its associated coils, is molded into a block ofplastic material 56. A transducer retaining spring 58 is secured to' thebody of the arm and extends outwardly over an edge of the plasticportion of the transducer unit 52. A substantially inverted-U-shapedfront plate 60 is secured to the face of the enlarged portion of the arm26 by a pair of screws 62. Between the transducer unit 52 and the frontplate 60 there is placed a rocker plate 64. A pair of adjusting screws66 extend through the front plate and press the rocker plate 64 againsta substantially flat face on the transducer unit, the remainder of thesurface of the transducer unit, as viewed in a transverse plane beingsubstantially circular. This arrangement provides means whereby thetransducer may be adjusted for azimuth. That is, the gap in the core maybe oriented at substantially 90 to the direction of travel of the soundtrack thereover.

The enlarged portion of the end of the arm 26 is provided with asubstantially inverted-U-shaped recess in the bottom thereof. The legsof this U-shaped recess are adapted to straddle the shaft 22 of thesound drum 14. The sound drum is a hollow cylindrical drum having anopen end which is open to the rear or towards the frame of the machine.The enlarged free end of the arm extends partially into the interior ofthe drum so that the transducer unit carried thereby is positioned withthe film contacting surface of the core assembly adjacent to the rearedge of the drum. In this position the transducer is adapted to engagethe sound track portion of the film which overhangs the rear edge of thedrum as it is being advanced thereover.

In addition to the magnetic transducer, the pivoted arm also carries amirror 68. This mirror is carried in a V-shaped recess in the extremeend of the arm 26, in such a position that a beam of light projectedfrom an exciter lamp unit 70 passes through andis modulated by anoptical sound track on the film being advanced around the drum. fallsupon the mirror 68 and is reflected thereby to a photocell 72.

One of the legs 74 defining the U-shaped recess in the bottom of thefree end of the arm is extended below the drum. There is a notch 76provided in the side of this extended leg. In order to effect a shiftfrom the magnetic sound system to the optical sound system or vice versathere is provided a mechanical switching arrangement. The switchmechanism includes a mounting plate 77 which is secured to the frame ofthe machine. Extending outwardly from the mounting plate is an operatinghandle or switch shaft 80, which is keyed to the knob 78, extendsthrough a suitable bearing 82 and terminates behind the mounting plate76 in an eccentric cam 84. The cam 84 rides in a transversely elongatedopening 86 in a switch plate 88. The arrangement of the cam and theopening in the switch plate is substantially equivalent to a scotchyoke. Rotation of the cam produces a vertical (as viewed in thedrawings) movement of the switch plate. An extension 90 on the switchplate terminates in a hook-like projection 92 which engages the edges ofthe notch 76 in the extended leg 74 of the arm 26.

A microswitch 94 is mounted on the back of the switch mounting plate 77and adapted to be actuated by the movement of the switch plate 88 ashereinafter further explained.

When the mounting assembly is placed on a machine as shown in Figure 1,the arm extends between the drum and the body of the machine, with aportion of the free end of the arm extending intothe rear open end ofthe drum. In this position, the transducer is placed adjacent to theopen end of the drum with its upper or film contacting surfaceprojecting slightly beyond the outer surface of the drum.

In order to adjust the position of the transducer so that the soundtrack on the film will engage the transducer at the non-magnetic gaptherein rather than on one of the shoulders thereof, the screw 36 isloosened, freeing the knurled cap member 34 fromthe pivot pin 24. Thusloosened. the knurled cap may be rotated about the screw 36. Since thepin 30'protruding from the end of the eccentric sleeve 28 rests in theradial recess 32 in the knurled cap, rotation of the cap will cause acorresponding movement of the sleeve about the pivot pin, causing alongitudinal movement of the arm 26 carrying the transducer. Thus thetransducer may be shifted with a transverse translational movement withrespect to the drum whereby the gap in the transducer may be adjustedwith respect to the curvature of the film defined by the drum to produceoptimum magnetic coupling between the transducer and the sound track.While the arm and the transducer have been thus adjusted, the screw maythen be tightened, locking the several parts in their respectivepositions.

To adjust the transducer radially of the sound drum to regulate thedistance that the transducer projects beyond the surface of the drum,the screw 44 with the eccentric head 46 is rotated. Since the eccentrichead 46 projects through the opening 48 in the arm, and the folded leafspring 38 presses the arm in a direction so that one side of the openingbears on the eccentric head, rotation of the screw 44 will cause arotational movement of the arm about the pivot pin 24 commensurate withthe shift in the direction of the eccentricity of the screw head. Solong as the are through which the arm is thus rotated is small, themovement of the transducer occasioned thereby will be substantiallyradial with respect to the drum. The

extent to which the transducer projects beyond the surface of the drum,together with the adjustment of the arm with respect to the folded leafspring, determines the pressure that the film contacting surface of thetransducer will exert upon the sound-track portion of the film. Theopening 48 in the arm through which the eccentric head of the screw 44projects is elongated to accommodate the longitudinal movement of thearm as previously described. The opening is also somewhat larger, in thedirection transverse of the arm, than the eccentric head of the screw.This arrangement permits a limited amount of freedom of movement of thearm against the bias pressure exerted thereon by the leaf spring. Thus,when the film is passing over the drum, the transducer is biased into aresilient engagement therewith.

If, through wear or other causes, it becomes necessary to readjust thetransducer, the foregoing procedure may be repeated, obviating thenecessity of remachining the parts.

When the apparatus has been set to operate with film having a magneticsound-track, the hook-like projections 92 on the extension of the switchplate 88 projects into the notch 76 in the leg 74 of the arm 26 withoutengaging the edges of the notch. That is, the hook-like member ridesfree in the notch. Thus, the arm, and hence the transducer, is free tofollow any irregularities in the film without interference from theswitch portion of the assembly.

The stroke or travel of the switch plate 88 is, however, greater thanthe intended amount of movement of the free end of the arm. Therefore,when the selector knob is turned to the optical" position and the cam 84causes the plate to move downward (as viewed in the drawings), theinitial movement of the plate takes up the slack between the hook-likeprojection and the lower edge of the notch. The remainder of thedownward stroke pulls the arm, against the force of the bias spring 38,to a position where the film contacting surface of the transducer isbelow the outer surface of the sound drum, hence out of engagement witha film being advanced over the drum.

The purpose served in moving the transducer out of engagement with filmwhen using a film bearing an optical sound track is twofold. First,running the film over the transducer while the transducer is not beingused would produce unnecessary wear on the face of the transducer.Second, in accordance with standard operating procedure, no stationarymember should be allowed to engage the optical sound-track portion of afilm while it is being run. This prevents scratching the film, whichscratches would produce distortion in the optical reproduction of therecorded signal.

When the arm has thus been shifted by the operation of the switchmechanism, the mirror 68 carried in the recess in the end of. the arm isin a position to reflect the light from the exciter lamp assembly 70onto the photocell unit 72. If, then, a film bearing an opticalsoundtrack is advanced over the sound drum, the film will pass betweenthe exciter lamp and the mirror and thereby modulate the light beam inaccordance with the signal on the optical sound-track.

The microswitch 94 mounted on the switch mounting plate is connected inseries with the exciter lamp of the optical system and, in the systemillustrated, should be of the type which is open when released. Thus,when the system is in position to respond to a magnetic soundtrack, theswitch plate does not bear on the actuator of the switch, therefore, theeXciter lamp is not energized. However, when the system is switched tooptical, the switch plate depresses the actuator of the microswitch,closing the circuit to the exciter lamp preparatory to operation with afilm bearing an optical sound-track.

What is claimed is:

1. A sound reproducing unit for magnetic film records comprising a sounddrum, means for advancing film over said drum, a shaft for said drum, abracket having a portion surrounding said shaft, an arm, pivot meansconnecting one end of said arm to said bracket at a point remote fromsaid drum, said arm having a portion at the other or free end thereofextending adjacent said drum, a magnetic transducer mounted on the freeend of said arm adjacent to said drum whereby said transducer is adaptedto engage a portion of a film being drawn over said drum, resilientmeans operatively coupled between said bracket and said arm for biasingsaid transducer into engagement with said film, and means including aneccentric member surrounding said pivot means for effecting anadjustment of said arm in a direction longitudinal thereof whereby saidtransducer may be adjusted with respect to the curvature of said drum.

2. The invention as set forth in claim 1 characterized by the additionof means including a second eccentric member for efiecting an adjustmentof said arm in a direction transverse thereof, said second eccentricmember being rotatably secured to said bracket, said arm having anelongated opening through which said eccentric member projects.

3. In sound motion picture apparatus of the type adapted for use withfilm bearing a magnetic sound-track, having a sound drum about whichsaid film is adapted to be advanced and a magnetic transducer adapted toengage the magnetic sound-track on said film adjacent said drum;mounting means for said transducer comprising a bracket, an arm, pivotmeans connecting one end of said arm to said bracket at a point remotefrom said drum, said arm having a portion at the other or free endthereof extending adjacent said drum, said transducer being mounted onsaid arm adjacent the free end thereof, resilient means operativelycoupled between said bracket and said arm for biasing said arm in arotational direction about said pivot with respect to said bracket, anadjustable stop means for determining the position of said arm withrespect to said bracket, said adjustable stop means comprising aneccentric member rotatably mounted on said bracket, said arm having anelongated opening therein through which said eccentric member projects,and means including an eccentric member surrounding said pivot means foreffecting adjustment of said arm in a direction longitudinal thereofwith respect to said bracket.

References Cited in the file of this patent UNITED STATES PATENTS2,003,434 Goldhammer June 4, 1935 2,257,028 Westerkamp Sept. 23, 19412,439,446 Begun Apr. 13, 1948 2,535,480 Begun Dec. 26, 1950 2,550,916Davis May 1, 1951 2,560,569 Hare June 17, 1951 2,585,913 Camras Feb. 19,1952 2,588,616 Carlson Mar. 11, 1952 2,605,364 Masterson July 29, 1952

